Casein coating composition and method of preparing the same



1,893,608, 2,023,389, and others has lt i cream, which is the source of the great bulk of Patented Au 1, 1939 I 2,167,752

CASEIN COATING COMPOSITION AND METHOD OF PREPARING THE SAIHE Charles G. Harford, Wollaston, Mass., assignor to Arthur D. Little, 1110., Cambridge, Mass, a corporation of Massachusetts No Drawing. Application August 3, 1937,

Serial No. 157,147

6 @laims. (Ell. l34-5l]) This invention relates to smooth viscous casein above-described type in a number of ways, and coating compositions and the like, and to meth p s s ertain advantages over h m, l ods or making them. now be pointed out. i

This application is, in part, a continuation oil n Carrying Out t s p the Casein used as my co-pending application Serial No. 105,081, the starting material should be wet or moist, and.

filed October 10, 1936, for Buttermilk casein solu- Should not have been reduced to dry fo t 5 tion. any stage in its manufacture from the original It is an object of this invention to manufacture source (skim milk, bu Whole milk, casein vehicles which are suitable ror use in the y b in t us k p w t or st, t as m preparation of coatings, such as water paints, mains in substantially the same swollen and disw and to manufacture stable coating compositions pe s d S e in Which it C n t Original from these vehicles. milk. Therefore, I find .it unnecessary to add Another object is to dispense with the necesswellin agents, as e Casein is dy Swollen; sity for using solvents or swelling agents in th also, I find it unnecessary to add solvents, which m preparation of such compositions. would be required if the casein were in dry form. w

A further object is to provide stable casein Y this P it is therefore possible to elimicoating compositions which, when dried, are more hate the 'coilvehtioiial p of fi d y the resistant to moisture than are the conventional casem- The t o Swelling e t d/ types of these coatings wherein solvents and/or vents is also avoided. And as a result of this m swelling agents are used in their preparation. pr r it is p i le to m a c s in c tin still another object is to utilize the solids of compos tion which. w e ied. is o resistant buttermilk in the preparation of casein comt tur t an onvent nal casein c p positions of the type herein described. tions using solvents and/or swelling agents, as

Other objects will appear fr th following these latter substances, being necessarily present disclosures. in the conventional product, retain their poten- In the past, the preparation of casein compotial solvent and /or swelling properties which besitions for use in making paints, coatings, fincome manifest when the product is subjected to ishings, etc., was generally accomplished by takllr ing dried casein, which had been prepared from A fur adva e of t pr s t invention skim milk by any one of a, number of processes, lies in the fact that it is suitable for preparing and treating this dried casein with an alkali or compos t o of the yp described fromv the alkaline substance to put it into solution. The n Obtained from buttermilk- This is of p resulting solutions were distinctly alkaline, and t cular p t owing t the t that such were subject to physical and chemical changes Casein, While available in large q y. has bee which made them unfit for use after the a hitherto of little commercial value. At present, 35

of a relatively short time (a few days, generally, buttermilk is a il -P c av little use, bein or sometimes hours). In recent years, however, com p y either as a source of f ed the work of Atwood, Iddjngs, a d Regnier, a for stock, or even discarded as worthless. This d ibe i ,5;v t t 1,50 ,031, is especially true with buttermilk from sour the development of acidic casein compositions buttermilk d which, when suitable materials of a bactericidal The Solids Obtained m u te ilk in the and fungicidal nature are included, retain .their manner herein described differ from ordinary stability over longperiods of time. casein in having appreciable quantities of asso- The casein compositions as prepared in acciated materials present, more especially albu- 45 cordance with the present invention are of this men, and fats and fat-like substances including latter general typei. e., they are stable, viscous lecithin. The fats and fat-like substances are dispersions or solutions, and are slightly acidic, Ofyaricus types, but all come under thegeneral havingapI-I range of between 446 and 7.0 (which term lipoids, which will be used hereinafter values. are respectively theisoelectn'c pointufor to designate them. .liipoids are the mix- 50 v casein andexactneutrality);or they may have a ture of fats, substances of fat-like nature such pHlvaiue; as high asa9 'or thereaboutsif properly as lipins, and other. substances obtained: in the ",bufiered, i. 3;." 1 Roese-Gottliebextractionprocedure (see Of- A i ,sflliis. invention,,howeve z, distinguishes from ficial and TentativeMethods of Analysis of the conventional acidic casein compositions of the Association of Official Agricultural Chemists,

4th ed.). Lipins are substances of a fat-like nature yielding on hydrolysis fatty acids or derivatives of fatty acids, and containing in their molecule either nitrogen or nitrogen and phosphorus. They include the phospholipins, such lecithin, cephalin, and sphingomyelin, and the galactolipins or cerebrosides (see Lecithin and Allied Substances by Hugh & J. S.' MacLean, 2nd ed., p. 3). The terms buttermilk solids, buttermilk casein and casein from buttermilk, as used herein, refer to the true casein together with these associated materials-the lipoids, albumen, and also the ash. The buttermilk casein does not necessarily contain all or even a major portion of the albumen .andlipoids present in the original milk, but it does contain significant amounts of them, as indicated below, I

whereas ordinary commercial caseins do not.

The successful commercial utilization of caseins relatively high in albumen and lipoids has not hitherto been accomplished, so far as I am aware. Caseins of this type, typically those obtained from buttermilk, contain at least about 4 or 5% lipoids (as determined by the Roese-Gottlieb method), as compared with between 0.5% and 2% in ordinary caseins. They also ordinarily contain significant amounts of albumen, up to about 10%. Ordinary caseins now commercially used have amounts of albumen, lipoid, etc.) too small to be of any significance. With casein of the type obtained'from buttermilk, however, these constituents have hitherto been a serious drawback to utilization. Thus, albumen, when precipitated by heating, is an irreversible colloid which, on drying, becomes dehydrated. By the term albumen I include as well other albuminous and protein materials in the buttermilk which act in the manner here defined with respect to albumen. In this dehydrated form (which is obtained when buttermilk casein is dried in the course of customary procedure) it is impractical to adequately re- -hydrate and redisperse the albumen at the pH values set forth herein, even when solvents and/ or swelling agents are used. If the albumen is kept wet, as during pasteurization, ordinary heating (say to 180 F.) does not markedly dehydrate it, although heating does precipitate and more or less denature it. In the precipitated wet state, however, the albumen is swollen, and is useful in the present process, which is not true if the albumen is dried after heat precipitation. Since I maintain the buttermilk solids obtained as herein described in a wet condition until after the final composition is formed, and the said solids may or may not have been through a pasteurization process, the difiiculties caused by dried albumen are avoided, and the albumen present provides certain advantages, such as improved water resistance of the final dried product.

If desired, albumen and/or lipoids may be added to the solids from skim milk, or even those from buttermilk, to give a high-albumen and/or high-lipoid casein which may be treated in accordance with the present invention.

While this invention, as already stated, is applicable to casein from milk whether whole, skim, or buttermilk, to give good and useful products, casein with associated solids, typically those solids associated with casein from buttermilk, impart certain additional qualities to the product which are not present when using ordinary dried casein. Thus, coating materials prepared as herein described, using casein and associated solids typicallyfrom buttermilk, are superior to those prepared from ordinary dried casein in their flowing and leveling (brushing) qualities (1. e., they spread more easily), in their resistance to foaming during preparation, and in their resistance to moisture when dried. The fats and fat like substances or lipoids retained in the product do not tend to separate out and appear on the surface, as would be expected from past experiences. The presence of the albumen appears to increase the water resistant character of the product.

In carrying out this invention, the casein and associated solids from skim milk, buttermilk, or other milk source are obtained by conventional procedure, as by acid precipitation (e. g., selfsouring, added acid, etc.). The liquid (whey) is separated from the precipitate, as its presence would be detrimental to the final product. The liquid to solids ratio is then adjusted to any suitable degree for making coatings-say about 4 or 5 to 1 for paint vehicles (which are customarily subsequently diluted). This adjustment may be made after the usual washing of the precipitate, or with a wash water, or otherwise as desired.

The process preferably comprises the acid precipitation, as by self-souring, of the casein and associated solids from buttermilk obtained from previously pasteurized cream. Albumen is thus obtained along with the casein and other associated solids such as the lipoids. The solids are kept in a wet state at all times. In this way, the

defects heretofore associated with buttermilk casein products are overcome and a superior coating composition is obtained.

If swelling agents and/or solvents are to be added in preparing the composition of this invention, it is desirable to heat the mixture containing them and the casein and water in order to promote the action of these solvents or swelling agents. About to hour of heating at say -160 is suflicient. While the solvents may contribute somewhat to ensuring a smooth com- .position, and both the swelling agents and the solvents to ensuring the desired viscosity, either or both may be dispensed with, as already stated, without any significant detriment to the product and in fact with certain advantages already pointed out. I

If a swelling agent is used, any of the customary materials such as sodium acetate, sodium formate,

lithiumchloride, etc., may be employed. As solvents, many alkalies are known and suitable, e. g., borax, trisodium phosphate, and various soaps and organic amines-or a strong alkali followed by a mild acid.

Whatever procedure is followed-whether or not swelling agents and/or solvents are usedthe resulting casein composition as prepared should have a pH lying between the isoelectric points for casein and water-i. e., between 4.6 and 7.0. When no solvents or swelling agents are used, the pH should be adjusted to fall within this range, if not already in it, but ordinarily it is. A higher pH (above 7.0) will result in a composition subject to the objections generally of the hitherto used alkaline casein solutions, unless proper buffering is done, as will be'described hereinafter. On the other hand, a pH below 4.6 has a tendency to agglomerate the casein and give an unsuitable product.

To make the casein paint or coating, the vehicle produced as above described is thoroughly mixed with a suitable pigment. Thus, for making. a white paint, 'Iitanox" (titanium dioxide pigment) may be added to the casein composition and passed, for example, through a conventional paint mill, whereupon it is ready for use. This thorough mixing with pigments acts to smooth out and homogenize the final coating composition. Without such thorough mixing, the resulting coating composition will not be smooth enough for most practical applications. It appears that the particles of the pigments act, while being mixed, to grind and homogenize the solids of the vehicle, thus producing a coating composition of the desired smoothness and uniformity.

As one specific example, of my procedure, the following will serve, using neither solvent nor swelling agent:

Vehicle Pounds Casein paste to give solid content on bone dry basis of 100 Enough water to give total water content of- 500 Pine oil 8 Fish i 40 Pigments Pounds Lithopone 4.90 Asbestineuflr 180 As another example, using a solvent, take the preceding example and add 8 lbs. borax in preparing the vehicle.

As another example, using a swelling agent, take either of the preceding examples and add lbs. sodium formate in preparing the vehicle.

The ingredients of the vehicle, in any of the examples, are mixed together, and, if swelling agents and/or solvents are used, the mixture is heatedat say 150-160 F. for about hour-- and then cooled to ordinary temperature. Heating is not necessary if no swelling agents or solvents are used. The pigments (white, in this instance, although colored pigments are used if desired) are then added, and thoroughly mixed with the vehicle. In the final product, the casein solids should generally equal about 12% to of the pigment solids, for best results. The product may be diluted, if desired, before application.

The fish oil acts as a plasticizer. Other plasticizers may be used if desired. The pine 011 imparts an agreeable odor, and also tends to serve as a bactericide. If it is desired to keep the paint over long periods of time, say for several months, a more effective egent such as sodium phenyl phenate, may be added, to act as both bactericide and fungicide.

There are two types of decomposition or deterioi'ation from which casein compositions of the kind herein described must be protected if they are to be kept for any length of time,-- growth ofbacteria and fungi, and proteolysis. The former is prevented by a preservative; the latter (at least in its ammonolysis aspects) by preparing the composiiton at a pH not in excess of 7.0. Prevention of these kinds of deterioration should be accomplished with respect to the original casein before preparation of the compositions herein described, if said casein is to be kept for any length of time before it is used. This is, obviously, accomplished by pH control and the use of a bactericide and fungicide.

A modification of the present process has already been suggestednamely the preparation of coating compositions having a pH value on the slightly alkaline side of neutrality. It is customarily held that casein solutions which are on the alkaline side of neutrality will readily deteriorate and become unfit for use in a relatively short. time,--even if bactericides and fungicides are used,because of ammonolysis. I find, however, that by properly buffering the casein coating solutions, prepared otherwise in accordance with this invention, I may make such solutions with a pH value up to about the point wheresubstantial ammonolysis takes place and ammonia is given ofi,--that is, in the neighborhood of pH=9 or somewhat higher. these compositions are thoroughly stable and have all the other desirable characteristics of those made in accordance with this invention at pH values below 7. Buffered solutions are those which tend to resist changes in pH value even when small amounts of acids or alkalies are added. By'preparing my solutions buffered, at pH values not in excess of about 9, I can make a casein coating composition which is on the alkaline side (e. g., with a pH value of say 8 or 9) but which, due to buffer action, resists any increase of pH value to the point where substan tial ammonolysis takes place. In the past, alkaline casein solutions made at pH=8 or 9 or thereabouts would become progressively more alkaline with the passage of time, until substantial ammonolysis took place, with decomposition of the solutions.

The buffer may be a separate agent, and added when the pigments are added or at any other desired time; or it may be the pigment itself. Thus, in the former procedure, a solution of boric acid and sodium hydroxide in the approximate weight-ratio of 3 parts of the former to one of the latter, may be added; while in the latter procedure, a pigment such as lithopone, used as in Furthermore,

the example already given, is a suitable buffer Except for this use of buffers with the consequent ability to prepare a solution having a pH value above 7 up to any point below that at which substantial ammonolysis takes place, my procedure for this modification is exactly the same as that previously described herein for preparing casein coating compositions and vehicles having pH valuesbetween 4.6 and 7.0.

While the preferred embodiment of the inventin is disclosed herein, it should be understood that this is by way of example and that I am limited only by the scope of the appended claims.

I claim:

1. The method of converting buttermilk casein and some of its accompanying solids into a smooth viscous liquid coating composiiton which consists in precipitating said casein and carrying down the precipitated casein and the accompanying solids, including lipoids in the proportions of about 4% or more of lipoids to 100% buttermilk casein, from their original accompanying whey, then adding an alkaline casein dissolving agent in sufiicient quantity to produce a solution with a pH of above '7, thoroughly mixing said vehicle in its wet state with pigments in the presence of a buffer substance acting to maintain a pH value below that at which substantial ammonolysis takes place, and maintaining enough water with the solids to prevent drying thereof until the final coating composition is completed.

2. The method of converting buttermilk casein and some of its accompanying solids into a smooth viscous liquid coating composition which consists in precipitating said casein and carrying down the precipitated casein and the acpanying whey, then adding an alkaline casein dissolving agent in suilicient quantity to produce a solution with a pH of above 7, thoroughly mixing said vehicle in its wet state with pigments in the presence of a buffer substance comprising a solution of boric acid and sodium hydroxide acting to maintain a pH value below that at which substantial ammonolysis takes place, and maintaining enough water with the solids to prevent drying thereof until the final coating composition is completed.

3.'The method of converting buttermilk casein and some of its accompanying solids into a smooth viscous liquid coating composition which consists in precipitating said casein and carrying down the precipitated casein and the accompanying solids, including lipoids in the proportions. ,of about 4% or more of lipoids to 100%'| buttermilk casein, from their original accompanying whey, then adding an alkaline casein dissolving agent in sufficient quantity to produce a solution with a pH of about 7, thoroughly mixing said vehicle in its wet state with pigments in the presence of a bufler substance comprising lithopone acting to maintain a pH value below that at which substantial ammonolysis takes place, and maintaining enough water with the solids to prevent drying thereof until the final coating composition is completed.

4. A smooth stable viscous liquid coating composition having a pH above 7 and below 9, comprising the reaction product of acid precipitated undried buttermilk solids including casein, albumen, and at least 4% lipoids, an alkaline casein dissolving agent and a butler substance, reacted together while the casein is in the undried state.

5. A smooth stable viscous liquid coating composition having a pH above '7 and below 9, comprising the reaction product of acid precipitated undried buttermilk solids including casein, albumen, and at least 4% lipoids, an alkaline casein dissolving agent and a buffer substance comprising lithopone, reacted together while the casein is in the undried state.

6. A smooth stable viscous liquid coating composition having a pH above 7 and below 9, comprising the reaction product of acid precipitated undried buttermilk solids including casein, albumen, and at least 4% lipoids, an alkaline casein dissolving agent and a buffer substance comprising a solution of boric acid and sodium hydroxide, reacted together while the casein is in the undried state.

CHARLES G. HARFORD. 

